An intensifying Hurricane Earl is pounding Puerto Rico and northern Lesser Antilles Islands with heavy rain and high winds this morning. The eye of Earl passed just north of Anguilla at 9am EDT, and Juliana airport on neighboring St. Martin Island recorded sustained winds of 47 mph, gusting to 68 mph at 8am EDT before going silent. An Air Force Hurricane Hunter aircraft currently in Earl just found a central pressure of 960 mb at 9:42 am EDT. This is a significant drop of 25 mb in 25 hours. Top flight level winds at 10,000 feet seen by the Air Force aircraft were 128 mph. Using the usual rule of thumb that the surface winds are 90% of the 10,000 foot flight level winds gives one surface winds of 115 mph, which is right at the border of Cat 2/ Cat 3 strength. Top winds seen at the surface by the Air Force's SFMR instrument were lower, 104 mph. Recent satellite imagery shows that Earl is not perfectly symmetrical--there is still fewer heavy thunderstorms on the hurricane's north side, suggesting that upper-level northerly winds are bringing 5 - 10 knots of wind shear to the storm.

Outlook for the Caribbean islands todayLatest radar animations out of Puerto Rico and St. Marten show that the eye of Earl is on track to pass just to the northeast of the islands of Anguilla, St. Maarten, and The Settlement in the British Virgin Islands today. The periphery of Earl's southern eyewall will probably bring Category 1 hurricane conditions to some of these islands today. NHC is giving its highest odds for hurricane-force winds to Saint Maarten--a 99% chance. These odds are 4% for St. Thomas in the Virgin Islands, and 2% for San Juan, Puerto Rico. The main threat to Puerto Rico will be heavy rains--up to eight inches in isolated areas. Earl's rains, in addition to causing flooding and dangerous landslides, will also help alleviate drought conditions that have affected many of the islands this year.

Intensity forecast for EarlWind shear as diagnosed by the latest SHIPS model forecast is nearly non-existent over Earl--just 3 knots--put is probably higher than that, based on the fact that the northern portion of Earl cloud pattern is ragged. Further evidence of this is the fact that Earl's eyewall had a gap in its west side, according to the latest report from the Hurricane Hunters. Ocean temperatures are a near-record 30°C, and very warm waters extend to great depth, resulting in a total ocean heat content highly favorable for rapid intensification. These nearly ideal conditions for intensification should bring Earl to Category 4 strength by Tuesday morning, and Category 5 is not out of the question. Earl should be able to maintain major hurricane status through Thursday, when it will make its closest approach to North Carolina. Sea surface temperatures are very warm, 29°C, along the U.S. East Coast, and wind shear is expected to remain low through Thursday. By Friday, when Earl will be making its closest approach to New England, wind shear will rise to a high 20 - 30 knots and ocean temperatures will plunge to 20°C, resulting in considerable weakening. Earl will still probably be a Category 2 hurricane on Friday, when it could potentially make landfall in Massachusetts or Nova Scotia, Canada.

Figure 2. Swath of surface winds from Earl predicted by the 2am EDT Monday August 30, 2010 run of NOAA's GFDL model. Hurricane force winds (yellow colors, 64 kt and above) are predicted to stay off the coast and tropical storm force winds (light green colors, 34 knots and above) are predicted to stay off the U.S. coast, but affect the coast of Canada. Image credit: Morris Bender, NOAA/GFDL.

Track forecast for EarlOnce Earl passes the Lesser Antilles, steering currents favor a northwesterly course towards North Carolina. History suggests that a storm in Earl's current location has a 25% chance of making landfall on the U.S. East Coast, and Earl's chances of making a U.S. landfall are probably close to that. None of the computer models show Earl hitting the U.S., but the storm will likely come uncomfortably close to North Carolina's Outer Banks and to Massachusetts. The latest set of model runs (2am EDT, or 6Z) project Earl will miss North Carolina by 200 - 300 miles on Thursday, and Massachusetts by a similar distance on Friday. Keep in mind that the average error in a 4 - 5 day NHC forecast is 200 - 300 miles, so the East Coast cannot breathe easily yet. The Outer Banks of North Carolina and Cape Cod, Massachusetts are both at the edge of the cone of uncertainty. NHC is giving Cape Hatteras a 9% chance of receiving hurricane force winds. These odds are 14% for Nantucket, 4% for Boston, and 2% for New York City. The main determinant of whether Earl hits the U.S. or not is a strong trough of low pressure predicted to move off the U.S. East Coast Friday. This trough, if it develops as predicted, should be strong enough to recurve Earl out to sea late in the week, with the storm just missing landfall in the U.S., but possibly making landfall in Nova Scotia, Canada.

Regardless of Earl's exact track, the U.S. East Coast can expect a long period of high waves beginning on Thursday. Significant beach erosion and dangerous rip current will be the rule, due to waves that will reach 10 - 15 feet in offshore waters (Figure 3.)

Figure 3. Wave forecast for 8am Friday, September 3, 2010, as produced by the 8pm EDT August 29 run of NOAA's Wavewatch III model. The model is predicting waves of 4 - 5 meters (13 - 16 feet) in the offshore waters from North Carolina to New Jersey.

Hurricane History for the northern Lesser AntillesThe last Cape Verdes-type hurricane to affect the Barbuda and the surrounding northern Lesser Antilles Islands was Hurricane Debby of 2000, which passed over the islands on August 28 as a Category 1 hurricane. Damage was less than $1 million, and no fatalities were reported. The last hurricane of any kind to pass through the northern Lesser Antilles Islands was Category 4 Hurricane Omar, on October 16, 2008. Omar took an unusual track, moving towards the northeast, and the storm's eyewall missed all of the islands. Omar did $80 million in damage to the Caribbean, mainly on the islands of Antigua, Barbuda, Dominica, the SSS Islands (Saba, St. Eustatius, and St. Maarten), and the U.S. Virgin Islands. No direct deaths were attributed to Omar, and the name Omar was not retired from the 6-year rotating list of hurricane names.

97LThe tropical wave (Invest 97L) now 1000 miles east of the Lesser Antilles Islands has a well-defined surface circulation and enough heavy thunderstorms to be classified as a tropical depression, if it can maintain that state for another six or so hours. Satellite loops show the surface circulation clearly, but also that heavy thunderstorm activity has been slow to build. The storm is experiencing low wind shear of less than 5 knots, and is over warm 29°C waters. The main impediment to development continues to be dry air associated with the Saharan Air Layer (SAL) surrounding the storm. The latest SHIPS model forecast calls for shear to stay in the low range, 5 - 10 knots, through Tuesday, and this should allow 97L to organize into a tropical depression today or Tuesday. NHC is giving 97L a 90% chance of developing into a tropical depression by Wednesday.

97L is moving quickly to the west, at about 20 mph. This means it is catching up to Earl, which has slowed down to 14 mph. By Tuesday night, Earl is expected to be a large and powerful major hurricane with a well-developed upper-level outflow channel heading clockwise out from Earl's center at high altitudes. These strong upper-level winds will bring high levels of wind shear, 20 - 30 knots, to 97L, and probably arrest the storm's development. The most likely scenario depicted in the computer models is for 97L to be drawn into the low pressure wake of Earl and pass to the northeast of the Lesser Antilles. Earl would then eventually destroy 97L through high wind shear, and by robbing the storm of its moisture. An alternative scenario is that 97L will stay far enough away from Earl that it will be able to pass through the northern Lesser Antilles islands as a tropical storm on Wednesday and Thursday, then bend northwestwards to potentially threaten the Bahamas and U.S. East Coast. There is a very high degree of uncertainty on what may happen to 97L. History suggests that a storm in 97L's current location has a 25% chance of making landfall on the U.S. East Coast.

Figure 4. Morning satellite image of 97L.

DanielleHurricane Danielle is on its way to oblivion over the cold North Atlantic waters, and is only of concern to shipping interests.

Elsewhere in the TropicsOver in the Western Pacific, tropical cyclone activity is ramping up, with two named storms expected to affect land this week. As is typical in a La Niña year, these storms have developed close to mainland Asia, and don't have a lot of time over water to intensify into strong typhoons. The storm of most concern is Typhoon Kompasu, which is expected to hit Okinawa today and recurve northward into Korea on Thursday. It now appears the Kompasu will not have major impacts on China's largest city, Shanghai. In the South China Sea, the fearsome sounding Tropical Storm Lionrock is forecast to hit the Chinese coast near Hong Kong on Tuesday, but is not predicted to develop into a typhoon.

The GFS model is predicting formation of a tropical depression off the coast of Africa about seven days from now.

Agreed - Never seen lightning in H...only transformer blowing up and that greenish light... :)

A lot depends on your location. I was on the south side of Wilma and had lightning/thunder/high winds/tornado activity all around. Katrina (CAT 1) passed the area with just wind and rain. It depends on the storm and which side you are on at the time, I guess.

Quoting connie1976:I am very sorry for all who will be affected by this storm...u all are in my prayers....BUT.......I am extremely happy that it is NOT coming to South Florida....I moved here 4 years ago and there hasn't been a hurricane here....I am keeping them all away!! lol :)

Yeah, that's what my ex-wife thought when bought a condo in Cutler Ridge in 1986. :-\

Quoting connie1976:I am very sorry for all who will be affected by this storm...u all are in my prayers....BUT.......I am extremely happy that it is NOT coming to South Florida....I moved here 4 years ago and there hasn't been a hurricane here....I am keeping them all away!! lol :)

Sssshhhhh!! Don't jinx us :)2005 was the worst. Just got home from adopting our daughter from China and Wilma decided to come by and say hi. No power for 2 VERY long weeks.We use to get excited at the thought of a storm but no more. It was scary!!

Agreed - Never seen lightning in H...only transformer blowing up and that greenish light... :)

Oh, and that "flip the switch" buzzing noise. Now I'm trying to remember the lightning. Of course, every single window was shuttered up and pitch black when the power went out so I don't think I would have seen or heard it over the wind noise

Quoting katrinakat5:nash you know what imtalking about not trying to scare the people telling it like it is...

Well, the FL solution is completely out. Not happening. I for one, am not taking the SC/NC border out of the equation just yet. Like I said, until he scoots N of my latitude, all it takes is a little stronger ridging coupled with a day late in the trough progression to cause some trouble this way.

Until Earl is north of my latitude I am not taking my eyes off of him. I have seen some goofy crap happen over the last few years. Systems that had W Coast of FL (where I used to live) dead to rights, to all of a sudden ending up 500 miles west of that point...

How you ask? Ridges and troughs. Ridge is "supposed to be" weak one day. The next day, track shifts like gangbusters because the trough weakens or stalls.

Those can't always be relied on. Sometimes the "backfire". I've had a bad shoulder ever since a young stud went bonkers from a hit of that stuff and reared up and flipped over backwards hard enough to pick me off the ground and break the snap on the end of the lead. Better ask Orcca for some Grizz stuff.

I am very sorry for all who will be affected by this storm...u all are in my prayers....BUT.......I am extremely happy that it is NOT coming to South Florida....I moved here 4 years ago and there hasn't been a hurricane here....I am keeping them all away!! lol :)

I'm beginning to wonder if Fiona will develop from 97L? For 3 days now it wants to develop but it but it refuses to organize. Now it is catching up to Earl and he just might put the kibosh on 97L. Also, the latest GFS does not develop 97L.

OK really this is my last post. GFS has been on again off again on 97L for days. It has been good in long term dev in CV storms, crap on short. Had Danielle eating Earl, then had Earl disappearing, then had Earl curving at something like 35w when it though D would curve at 40. Until a center does or doesn't form, or until it's 2 days out, forget the models and look at the synoptic pattern. NHC may be overly bullish on model tracks, but they are bearish on formation. And even they say 90%. It may not form, just if you're in Vegas you play the don't pass cause the best odds pay off over time, and 97L is likely to become Fiona. What she is? Who knows. Euro has been locked on to formation, but has bounced in the last day from FL, to NC, to FL Keys, to recurve to sea; so when I get up in 6 hours I fully expect next Euro to say it hits Japan. And if it never forms it never forms, just conditions and synoptic pattern are favorable so for GA south and GOM crowd it holds more credence than the GFS gulf ghost storm it picked up from the old CMC runs.